A belt or chain tensioner includes a tension head engageable with a chain, belt or the like of a chain and belt drive and a tension piston on which the tension head is carried. The tension piston is longitudinally slidable in a guide body which is simultaneously a mounting element and is acted on by at least one tension spring engaged with it which is supported at its other end on the base of the guide body.
The belt and chain tension producing apparatus taught in German Utility Model No. 78 09 294 has for the most part a parallelepiped shaped tension piston which is slidable in a continuous smooth wall closed guide housing which is closed from below by a base plate and out of which the tension piston under the compressive force of the tension spring projects, carrying the tension head which presses against the chain or belt.
The belt or chain engaging member is provided with a curved sliding rail for use with a chain drive which can contact the chain of a chain drive while a tension head with a corresponding roller can be used for a belt drive. Since the spring or springs and the piston are coplanar with this rail or roller, this known belt or chain tension producing apparatus has a significant height or length which requires an appropriate space behind the chain or belt. For narrow space conditions and/or sharp turns of the chain and/or belt this known tension producing apparatus is not suitable.